Performance Evaluation of Underwater Wireless Optical Communication System by Varying the Environmental Parameters

Abstract

Underwater wireless optical communication (UWOC) has been considered a promising technology for high-speed underwater transmission. Some Gb/s level UWOC systems applying visible light have been demonstrated with a transmission distance of several meters or more. Many of the previous works focus on the advanced technologies to push the systems’ capacity–distance performance. However, practical environmental factors issue such as flow turbulence and temperature variation are seldom studied through specific statistical/theoretical models. In this paper, a UWOC system using a 450 nm blue light laser source was set up using a 1.5-m water tank with mirrors located on both sides for single or multiple reflections corresponding to different transmission distances. The blue laser was modulated by a 1.25 Gbps NRZ-OOK format with PRBS of 7, 24 or 31, respectively, for system performance comparison. The bit error rate (BER) values were measured in 1.5, 3.0 and 6 m, respectively, for system evaluation. At room temperature, the BER value was down to 10 × 10−8 for a 1.25 Gbps data rate in a 6 m transmission. Then, the UWOC transmission system experiment was carried out under several environmental parameters such as temperature, turbulence, artificial seawater by adding salt to simulate practical application in river or sea. When a submerged motor with an output of 1200 L/h was used as a water flow turbulence source, the impact to BER and transmission quality was negligible. For the temperature change issue, the experiment shows that around the original temperature of 25 °C had the best BER as compared to other temperature ranges from 10 to 50 °C. For artificial seawater issues by adding salt to simulate the real seawater environment. The transmission distance was only 3-m instead of 6 m, mainly due to particle scattering and water disturbance. With the motor pump on, the power penalty was 1 dB at 10 × 10−8 BER when compared to the motor pump off.

An Alternative Experimental Method for Determination of Light Beam Attenuation Coefficient in Underwater Wireless Optical Communication

“…Li et al [14] determined the effects of environmental factors such as temperature, turbulence, and salinity which cause attenuation in underwater optical communication systems. A temperature of 25 °C has a good performance.…”

Deep Learning-Assisted Index Estimator for Generalized LED Index Modulation OFDM in Visible Light Communication

“…Visible light communication (VLC) is a promising alternative for complementing the overcrowded radio frequency bandwidth of wireless communication owing to its license-free operations, relative low cost, high spatial diversity, high bandwidth efficiency, and electromagnetic interference-free transmission [1][2][3][4][5][6][7]. Orthogonal frequency division multiplexing (OFDM) has been extensively used in VLC to maintain a better transmission rate due to its high spectral efficiency and low-complexity implementation to achieve better transmission rates [8,9].…”